Systems and methods that use natural resources, such as sunlight and/or water, to catalyze the formation of fuels and other useful substances show tremendous potential. In particular, the use of naturally occurring systems, such as photosystem II (PSII), which is a protein complex involved in photosynthesis in certain plants, algae, and cyanobacteria, to produce biofuels such as diatomic hydrogen gas (H2) has been appealing. However, existing attempts to use such systems have suffered a number of problems. For example, PSII can result in the formation of both diatomic oxygen gas (O2) and diatomic hydrogen gas (H2), raising safety concerns. Additionally, the presence of diatomic oxygen gas appears to inhibit the activity of the enzyme that catalyzes the formation of diatomic hydrogen gas. Accordingly, improved systems and methods are needed.